Semiconductor device, solid state image pickup device and manufacturing method thereof

ABSTRACT

A semiconductor device that contains photodiodes whose sensitivity and storage capacity can be increased, and a solid-state image pickup device formed by arranging the photodiodes in an array and its manufacturing method. A first semiconductor region  11  of a second conductivity type is formed on the principal surface of a semiconductor substrate  10  of a first conductivity type. A pixel separating region  14  of the first conductivity type is formed to penetrate through the first semiconductor region  11  to separate the regions of the adjacent photodiodes PD. A second semiconductor region  15  of the second conductivity type used to drain excess charge is formed in semiconductor substrate  10  at a position away from the junction surface between semiconductor substrate  10  and the first semiconductor region  11  and below the junction surface.

FIELD OF THE INVENTION

The present invention pertains to a semiconductor device, and a solid-state image pickup device and its manufacturing method. In particular, the present invention pertains to a semiconductor device that contains photodiodes, and a solid-state image pickup device and its manufacturing method.

BACKGROUND OF THE INVENTION

A semiconductor photodiode is a diode that generates electric current upon receiving light. It is widely used as a light-receiving element for CCD sensors, CMOS sensors or other solid-state image pickup devices. A photodiode is made up of pn junction semiconductors. When the pn junction is reverse-biased and a high electric field is applied, the depletion layer widens. Incident light is absorbed mainly in the depletion layer and generates electron-hole pairs. The obtained charge is held by the potential generated in the photodiode and is detected as current or voltage. In a solid-state image pickup device, pixels having diodes with the aforementioned configuration are arranged in an array pattern to form the light-receiving part.

When a high-intensity light is irradiated on a given pixel in a solid-state image pickup device having the aforementioned photodiodes, if the generated photocharge exceeds the charge storage capacity of the photodiode, the charge will overflow from said pixel to adjacent pixels. This phenomenon is known as blooming. For solid-state image pickup device, overflow drain (OD) that drain the excess photocharge that had saturated a pixel is widely used as an anti-blooming (AB) structure used for suppressing the occurrence of blooming. Overflow drains include lateral overflow drains (LOD) that drain the excess photocharge in the in-plane direction of the principal surface of a substrate and vertical overflow drains (VOD) that discharge the photocharge in the direction perpendicular to the principal surface of the substrate and toward the substrate.

FIG. 5(A) is a plan view illustrating a photodiode and the LOD part set next to it in a conventional CCD solid-state image pickup device. FIG. 5(B) is the cross-sectional view along X-X′ in FIG. 5(A).

For example, in the photodiode PD region that constitutes each pixel PX, n-type semiconductor region 101 and p-type semiconductor region 102 are formed on p-type semiconductor substrate 100 to form a pn junction that constitutes photodiode PD. For example, the photodiodes PD of various pixels PX are formed adjacent to each other. A pixel separating region I constituted with a p-type semiconductor region is formed between adjacent photodiodes PD. Also, a lateral overflow drain LOD is arranged in said pixel separating region. The LOD has an n-type semiconductor region 103 formed on the inner side and a p-type semiconductor region 104 formed on the outer side.

FIG. 5(C) is a potential diagram for the cross section shown in FIG. 5(B). The highest potential from the surface to a part deep inside the substrate at a certain point on X-X′ is taken as the potential at that point. Said potential diagram is obtained by plotting each point on X-X′. The positive (+) potential direction is downward. In this case, on the cross section X-X′ that crosses the LOD as described above, as indicated by potential P1 in FIG. 5(C), a potential barrier is formed in the part where p-type semiconductor region 104 is formed. The photocharge (photoelectrons) are stored in the potential valley on the PD side.

A prescribed voltage VAB is applied to said n-type semiconductor region 103. As indicated by potential P2 in FIG. 5(C), the potential of the n-type semiconductor region 103 part is shifted to the high potential side. At the same time, the barrier of the potential of the p-type semiconductor region 104 part is modulated to the high potential side. At that time, when the charge C stored in the potential valley on the PD side overflows, the charge will pass the potential barrier (AB barrier) of the p-type semiconductor region 104 part to drain into n-type semiconductor region 103 (AB drain).

The LOD with the aforementioned configuration is used to drain the charge. It is insensitive to the storage of charge or light. Consequently, in order to increase the sensitivity of the photodiode, and hence the sensitivity of the solid-state image pickup device, it is desired to form it with a layout that is as small as possible.

However, miniaturization is difficult since p-type semiconductor region 104 acting as the AB barrier is formed around n-type semiconductor region 103 acting as the AB drain. Consequently, the width of the LOD region becomes larger than the width of pixel separating region I as shown in FIG. 5(A), which leads to a decrease in the sensitivity of the photodiode and solid-state image pickup device and a decrease in storage capacity.

The other well-known OD structure is VOD. The VOD, however, usually has an n-type substrate to discharge charge to the side of the n-type substrate. Said LOD is usually used for photodiodes having a p-type substrate. Photodiodes using an n-type substrate are undesirable if an application demands increased sensitivity, since they have lower sensitivity, especially on the long wavelength side, than photodiodes using a p-type substrate.

A general object of the present invention is to solve the aforementioned problem by providing a semiconductor device having photodiodes that can increase the sensitivity and storage capacity, a solid-state image pickup device formed by arranging said photodiodes in an array, and its manufacturing method.

SUMMARY OF THE INVENTION

This and other objects and features are prescribed in accordance with one aspect of the present invention by a solid-state image pickup device formed by arranging plural photodiodes separated by pixel separating regions in an array pattern, characterized by having a semiconductor substrate of a first conductivity type, a first semiconductor region of a second conductivity type formed on the principal surface of said semiconductor substrate, a pixel separating region of the first conductivity type formed to penetrate through said first semiconductor region to separate the adjacent regions of said photodiodes, a second semiconductor region of the second conductivity type that is separated from the junction surface between said semiconductor substrate and the first semiconductor region and is formed in said semiconductor substrate below said junction surface and is used to drain excess charge.

For the aforementioned solid-state image pickup device of the present invention, the first semiconductor region of the second conductivity type is formed on the principal surface of the semiconductor substrate of the first conductivity type. The pixel separating region of the first conductivity type is formed to penetrate through said first semiconductor region to separate the adjacent regions of said photodiodes. The second semiconductor region of the second conductivity type is separated from the junction surface between said semiconductor substrate and the first semiconductor region and is formed in said semiconductor substrate below said junction surface and is used to drain excess charge.

For the solid-state image pickup device of an aspect of the present invention, said second semiconductor region is formed below said pixel separating region. Also, a third semiconductor region of the first conductivity type may be formed on the surface layer of the first semiconductor region.

Another aspect of the present invention provides a semiconductor device on which photodiodes are formed, characterized by having a semiconductor substrate of a first conductivity type, a first semiconductor region of a second conductivity type formed on the principal surface of said semiconductor substrate, and a second region of the second conductivity type that is separated from the junction surface between said semiconductor substrate and the first semiconductor region and is formed in said semiconductor substrate below said junction surface and is used to drain excess charge.

For the aforementioned semiconductor device of the present invention, the first semiconductor region of the second conductivity type is formed on the principal surface of the semiconductor substrate of the first conductivity type, and the second region of the second conductivity type is separated from the junction surface between said semiconductor substrate and the first semiconductor region and is formed in said semiconductor substrate below said junction surface and is used to drain excess charge. For the semiconductor device of an aspect of the present invention, a third semiconductor region of the first conductivity type may be formed on the surface layer of the first semiconductor region.

Also, an aspect of the present invention provides a solid-state image pickup device manufacturing method used for manufacturing a solid-state image pickup device formed by arranging plural photodiodes separated by pixel separating regions in an array, characterized by having the following steps: a first semiconductor region of a second conductivity type is formed on the principal surface of a semiconductor substrate of a first conductivity type; a pixel separating region of the first conductivity type is formed to penetrate through said first semiconductor region to separate the adjacent regions of said photodiodes; a second semiconductor region of the second conductivity type used to drain excess charge is formed away from the junction surface between said semiconductor substrate and said first semiconductor region in the semiconductor substrate below said junction surface.

In the aforementioned solid-state image pickup device manufacturing method of the present invention, the first semiconductor region of the second conductivity type is formed on the principal surface of the semiconductor substrate of the first conductivity type, and the pixel separating region of the first conductivity type is formed to penetrate through the first semiconductor region to separate the regions of the adjacent photodiodes. Also, the second region of the second conductivity type is separated from the junction surface between said semiconductor substrate and the first semiconductor region and is formed in said semiconductor substrate below said junction surface and is used to drain excess charge.

In the aforementioned solid-state image pickup device manufacturing method of an aspect of the present invention, said second semiconductor region may be formed below said pixel separating region in the step used to form said second semiconductor region. In addition, the method may also contain a step for forming a third semiconductor region of the first conductivity type on the surface layer of said semiconductor region.

Also, an aspect of the present invention provides a semiconductor device manufacturing method for manufacturing a semiconductor device on which photodiodes are formed, characterized by the following steps: a first semiconductor region of a second conductivity type is formed on the principal surface of a semiconductor substrate of a first conductivity type; and a second semiconductor region of the second conductivity type is separated from the junction surface between said semiconductor substrate and the first semiconductor region and is formed in said semiconductor substrate below said junction surface and is used to drain excess charge.

In the aforementioned semiconductor device manufacturing method of the present invention, the first semiconductor region of the second conductivity type is formed on the principal surface of the semiconductor substrate of the first conductivity type, and the second semiconductor region of the second conductivity type is separated from the junction surface between said semiconductor substrate and the first semiconductor region and is formed in said semiconductor substrate below said junction surface and is used to drain excess charge.

The aforementioned semiconductor device manufacturing method of an aspect of the present invention may also contain a step for forming a third semiconductor region of the first conductivity type on the surface layer of said semiconductor region.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1(A) is the plan view of the photodiode and overflow drain part in the solid-state image pickup device disclosed in the first embodiment of the present invention. FIG. 1(B) is the cross-sectional view along X-X′ in FIG. 1(A). FIG. 1(C) is a potential diagram at the cross section shown in FIG. 1(B).

FIGS. 2(A)-(C) are cross-sectional views illustrating the process of the method for manufacturing the solid-state image pickup device disclosed in the first embodiment of the present invention.

FIG. 3(A) is the plan view of the photodiode and overflow drain part in the solid-state image pickup device disclosed in an embodiment of the present invention. FIG. 3(B) is a cross-sectional view along X-X′ in FIG. 3(A). FIGS. 3(C) and (D) are the potential diagrams obtained by simulation.

FIG. 4(A) is the plan view of the photodiode and overflow drain part in the solid-state image pickup device disclosed in the second embodiment of the present invention. FIG. 4(B) is the cross-sectional view along X-X′ in FIG. 4(A).

FIG. 5(A) is the plan view of the photodiode and overflow drain part in the solid-state image pickup device disclosed in a conventional example. FIG. 5(B) is the cross-sectional view along X-X′ in FIG. 5(A). FIG. 5(C) is the potential diagram on the cross section shown in FIG. 5(B).

REFERENCE NUMERALS AND SYMBOLS AS SHOWN IN THE DRAWINGS

In the figures, 10 represents a p-type semiconductor substrate, 11 an n-type semiconductor region (first semiconductor region), 12 a p-type semiconductor region (third semiconductor region), 13 a resist film, 14 a pixel separating region, 15 an n-type semiconductor region (second semiconductor region), 16 an n-type semiconductor region, 100 a p-type semiconductor substrate, 101 an n-type semiconductor region, 102 a p-type semiconductor region, 103 an n-type semiconductor region, 104 a p-type semiconductor region, C a charge, LOD a lateral overflow drain, I a pixel separating region, P1, P2 a potential, PD a photodiode, PX a pixel.

DESCRIPTION OF THE EMBODIMENTS

For the solid-state image pickup device of an aspect of the present invention, the second semiconductor region of the second conductivity type is formed as a region for draining excess charge in the semiconductor substrate away from the junction surface between the semiconductor substrate and the first semiconductor region at a location below said junction surface. The width of the pixel separating region can be set to the smallest level required. In this way, the sensitivity of the photodiodes that constitute the solid-state image pickup device can be improved and the storage capacity increased.

For the semiconductor device of an aspect of the present invention, the second semiconductor region of the second conductivity type is formed as a region for draining excess charge in the semiconductor substrate away from the junction surface between the semiconductor substrate and the first semiconductor region below said junction surface. The width of the region that separates the photodiodes can be set to the smallest level required. In this way, the sensitivity of the photodiodes can be improved and the storage capacity increased.

According to the solid-state image pickup device manufacturing method of an aspect of the present invention, since the second semiconductor region of the second conductivity type is formed as a region for draining excess charge in the semiconductor substrate away from the junction surface between the semiconductor substrate and the first semiconductor region below said junction surface, the width of the pixel separating region can be set to the smallest level required. In this way, the sensitivity of the photodiodes that constitute the solid-state image pickup device can be improved and the storage capacity increased.

According to the semiconductor device manufacturing method of an aspect of the present invention, since the second semiconductor region of the second conductivity type is formed as a region for draining excess charge in the semiconductor substrate away from the junction surface between the semiconductor substrate and the first semiconductor region below said junction surface, the width of the region that separates the photodiodes can be set to the smallest level required. In this way, the sensitivity of the photodiodes can be improved and the storage capacity increased.

Embodiments of the solid-state image pickup device and its manufacturing method disclosed in the present invention will be explained below with reference to figures.

First Embodiment

FIG. 1(A) is the plan view of a photodiode and an overflow drain part in a solid-state image pickup device, such as a CCD sensor, disclosed in this embodiment. FIG. 1(B) is a cross-sectional view along X-X′ in FIG. 1(A).

The solid-state image pickup device disclosed in this embodiment is formed by arranging plural photodiodes separated by pixel separating regions in an array pattern. For example, in photodiode PD region that constitutes each pixel PX, n-type semiconductor region (first semiconductor region) 11 is formed on p-type semiconductor substrate 10 to form a pn junction that constitutes photodiode PD. For example, the photodiodes PD of pixels PX are formed adjacent to each other. A p-type pixel separating region 14 is formed to penetrate through n-type semiconductor region 11 to separate the regions of the adjacent photodiodes PD. Three pixels PX are shown in FIG. 1(A). Also, for example, an n-type semiconductor region (second semiconductor region) 15 is formed at a prescribed distance D away from the junction surface between p-type semiconductor substrate 10 and n-type semiconductor region 11 in p-type semiconductor substrate 10 below said junction surface.

N-type semiconductor region 15 in p-type semiconductor substrate 10 is formed to be connected to n-type semiconductor region 16. A prescribed potential of several V is applied to n-type semiconductor region 16. In the solid-state image pickup device disclosed in this embodiment, for example, n-type semiconductor region 15 is formed below pixel separating region 14. The side surface of n-type semiconductor region 15 is positioned almost on the same plane as the side surface of pixel separating region 14. Also, for example, p-type semiconductor region (third semiconductor region) 12 is formed on the surface layer of n-type semiconductor region 11.

FIG. 1(C) is the potential diagram on the cross section shown in FIG. 1(B). The highest potential from the surface to a part deep in the substrate at a certain point along X-X′ is taken as the potential at that point. Said potential diagram is obtained by plotting each point along X-X′. The positive (+) potential direction is down.

In this case, as shown by potential P1 in FIG. 1(C), a potential barrier is formed at the position of the side surface of n-type semiconductor region 15. The photocharge (photoelectrons) is stored in the potential valley on the PD side. When a prescribed voltage VAB is applied to n-type semiconductor region 15 via n-type semiconductor region 16 as described above, as shown by potential P2 in FIG. 1(C), the potential in the region where n-type semiconductor region 15 is formed is shifted to the high potential side. At the same time, the barrier of the potential at the position of the side surface of n-type semiconductor region 15 is modulated to the high potential side. If charge C stored in the potential valley on the PD side overflows, the charge passes the potential barrier (AB barrier) at the position of the side surface of n-type semiconductor region 15 and drains into n-type semiconductor region 15 (AB drain).

For the solid-state image pickup device disclosed in this embodiment, n-type semiconductor region 15 is formed as a region for draining excess charge in the p-type semiconductor substrate at a location away from the junction surface of p-type semiconductor substrate 10 and n-type semiconductor region 11 and below said junction surface. Since the conventional LOD is not needed, the width of pixel separating region 14 can be set to the minimum level required. In this way, the sensitivity of the photodiodes that constitute the solid-state image pickup device can be improved and the storage capacity increased. Also, since the solid-sate image pickup device disclosed in this embodiment can be constituted using a p-type semiconductor substrate, the sensitivity on the long wavelength side can be increased. For example, the sensitivity with respect to light with a wavelength of 700 nm is twice as high as that of a photodiode using an n-type substrate having the conventional VOD.

The solid-state image pickup device of the present invention can be formed by arranging plural photodiodes having the aforementioned overflow drain in an array pattern. It can be used for CCD sensors, CMOS sensors, etc.

In the following, the solid-state image pickup device manufacturing method disclosed in this embodiment will be explained.

FIGS. 2(A)-(C) are cross-sectional views illustrating the process of the solid-state image pickup device manufacturing method disclosed in this embodiment.

First, as shown in FIG. 2(A), n-type semiconductor region (first semiconductor region) 11 is formed on the principal surface of p-type semiconductor substrate 10. P-type semiconductor region (third semiconductor region) 12 is formed on the surface layer of n-type semiconductor region 11.

Next, as shown in FIG. 2(B), for example, a resist film 13 is formed in a pattern that opens the element separating region by means of photolithography. By injecting the ions of a p-type impurity, p-type pixel separating region 14 is formed to penetrate through n-type semiconductor region 11 to separate the regions of the adjacent photodiodes.

Next, as shown in FIG. 2(C), for example, said resist film 13 is used and the ions of an n-type impurity are injected at a higher energy level than that used to form pixel separating region 14. As a result, n-type semiconductor region (second semiconductor region) 15 is formed as a region for draining excess charge in semiconductor substrate 10 at a position away from the junction surface between p-type semiconductor substrate 10 and n-type semiconductor region 11 and below said junction surface. As shown in FIG. 2(C), when pixel separating region 14 and n-type semiconductor region 15 are formed using said resist film 13, n-type semiconductor region 15 can be formed easily below pixel separating region 14. For example, the side surface of n-type semiconductor region 15 can be positioned on almost the same plane as the side surface of pixel separating region 14. In fact, since the impurities of n-type semiconductor region 15 injected into the lower levels have a higher degree of diffusion, there might be an interposed part between n-type semiconductor region 11 and n-type semiconductor region 15. This, however, does not change the fact that the potential shown in FIG. 1(C) can be obtained so that the desired overflow drain function can be realized.

According to the solid-state image pickup device disclosed in this embodiment, n-type semiconductor region 15 is formed as a region for draining excess charge in the p-type semiconductor substrate at a position away from the junction surface of p-type semiconductor substrate 10 and n-type semiconductor region 11 and below said junction surface. Therefore, the conventional LOD is not needed, and the width of pixel separating region 14 can be set to the minimum level required. In this way, the sensitivity of the photodiodes that constitute the solid-state image pickup device can be improved and the storage capacity increased. Also, since the solid-sate image pickup device disclosed in this embodiment can be constituted using a p-type semiconductor substrate, the sensitivity on the long wavelength side can be increased.

The potentials of the photodiodes in the solid-state image pickup device disclosed in the aforementioned embodiment were derived by means of simulation.

FIG. 3(A) is a plan view of the photodiodes and the overflow drain part in the solid-state image pickup device disclosed in this embodiment. FIG. 3(B) is the cross-sectional view along X-X′ in FIG. 3(A).

In the photodiode PD region constituting each pixel PX, n-type semiconductor region 11 was formed on p-type semiconductor substrate 10. P-type pixel separating region 14 was formed to penetrate through n-type semiconductor region 11 to separate the regions of adjacent photodiodes PD. Below pixel separating region 14, n-type semiconductor region 15 was formed as a region for draining excess charge in p-type semiconductor substrate 10 at a position away from the junction surface between p-type semiconductor substrate 10 and n-type semiconductor region 11 and below said junction surface. For the aforementioned configuration, the potential diagram obtained from the simulation result when a potential was applied to n-type semiconductor region 15 is shown in FIG. 3( c). The simulation result in the state when a prescribed positive potential was applied is shown in FIG. 3(D). The potential is shown as a relative value where the downward direction is the positive (+) direction.

As shown in FIGS. 3(C) and (D), a potential barrier was formed at the position of the side surface of n-type semiconductor region 15. Its height was modulated by the potential applied to n-type semiconductor region 15. It was confirmed that a potential that could function as an overflow drain for anti-blooming was obtained. Also, in the simulation for 3×3 μm pixels, the solid-state image pickup device disclosed in this embodiment showed a 20% increase in both sensitivity and charge storage capacity compared with the solid-state image pickup device using the conventional LOD.

Second Embodiment

FIG. 4(A) is the plan view of the photodiodes and the overflow drain part in the solid-state image pickup device, such as a CCD sensor, disclosed in this embodiment. FIG. 4(B) is the cross-sectional view along X-X′ in FIG. 4(A).

Unlike the first embodiment, n-type semiconductor region (second semiconductor region) 15 used as the region for draining excess charge is formed below n-type semiconductor region (first semiconductor region) 11 instead of below pixel separating region 14. In this case, n-type semiconductor region 15 is also formed at a prescribed distance D away from the junction surface between p-type semiconductor substrate 10 and n-type semiconductor region 11 and below said junction surface. In the solid-state image pickup device disclosed in this embodiment, a potential barrier can also be formed for the charge located at a prescribed distance D away from the junction surface. The height of the barrier is modulated by the potential applied to n-type semiconductor region 15. Since the conventional LOD is not needed, the width of pixel separating region 14 can be set to the minimum level required. In this way, the sensitivity of the photodiodes that constitute the solid-state image pickup device can be improved and the storage capacity increased.

The present invention is not limited to the explanation above. For example, the present invention can be applied not only to CCD sensor and other solid-state image pickup devices but also to all kinds of semiconductor devices having photodiodes. That is, a first semiconductor region of a second conductivity type is formed on the principal surface of a semiconductor substrate of a first conductivity type, and a second semiconductor region of the second conductivity type is formed as a region for draining excess charge in the semiconductor substrate at a position away from the junction surface between the semiconductor substrate and the first semiconductor region and below said junction surface.

The aforementioned semiconductor device can be manufactured by forming a first semiconductor region of a second conductivity type on the principal surface of a semiconductor substrate of a first conductivity type and forming a second semiconductor region of the second conductivity type as a region for draining excess charge in the semiconductor substrate at a position away from the junction surface between the semiconductor substrate and the first semiconductor region and below said junction surface.

Other changes can be made as long as they do not deviate from the main point of the present invention. The solid-state image pickup device of the present invention can be used for CCD sensors, CMOS sensors, or other solid-state image pickup devices. Also, the semiconductor device of the present invention can be used for semiconductor devices that contain photodiodes. The solid-state image pickup device manufacturing method of the present invention can be used to manufacture CCD sensors, CMOS sensors, or other solid-state image pickup devices. Also, the semiconductor device manufacturing method of the present invention can be used to manufacture semiconductor devices that contain photodiodes. 

1. A solid-state image pickup device comprising: plural photodiodes separated by pixel separating regions in an array pattern; a semiconductor substrate of a first conductivity type; a first semiconductor region of a second conductivity type formed on the principal surface of said semiconductor substrate; a pixel separating region of the first conductivity type formed to penetrate through said first semiconductor region to separate the adjacent regions of said photodiodes; and a second semiconductor region of the second conductivity type that is separated from the junction surface between said semiconductor substrate and the first semiconductor region and is formed in said semiconductor substrate below said junction surface and is used to drain excess charge.
 2. The solid-state image pickup device described in claim 1 wherein said second semiconductor region is formed below said pixel separating region.
 3. The solid-state image pickup device described in claim 1 wherein a third semiconductor region of the first conductivity type is formed on the surface layer of the first semiconductor region.
 4. A semiconductor device on which photodiodes are formed, comprising: a semiconductor substrate of a first conductivity type; a first semiconductor region of a second conductivity type formed on the principal surface of said semiconductor substrate; and a second region of the second conductivity type that is separated from the junction surface between said semiconductor substrate and the first semiconductor region and is formed in said semiconductor substrate below said junction surface and is used to drain excess charge.
 5. The semiconductor device described in claim 4 wherein a third semiconductor region of a first conductivity type is formed on the surface layer of said first semiconductor region.
 6. A solid-state image pickup device comprising: a first semiconductor layer of a first conductivity type; a second semiconductor layer and a third semiconductor layer of a second conductivity type formed adjacent to each other on said first semiconductor layer; a fourth semiconductor layer of the first conductivity type formed on said first semiconductor layer and positioned between said second and third semiconductor layers; a fifth semiconductor layer of the second conductivity type formed away from said second, third, and fourth semiconductor layers in said first semiconductor layer; a first light-receiving element comprised of said first and second semiconductor layers; and a second light-receiving element comprised of said first and third semiconductor layers.
 7. The solid-state image pickup device described in claim 6 wherein said fifth semiconductor layer is formed below said fourth semiconductor layer.
 8. The solid-state image pickup device described in claim 6 further comprising a sixth semiconductor layer of the first conductivity type is formed on said second, third, and fourth semiconductor layers.
 9. The solid-state image pickup device described in claim 6 further comprising a seventh semiconductor layer of the second conductivity type that is electrically connected to said fifth semiconductor layer, and a prescribed voltage is applied to said fifth semiconductor layer.
 10. The solid-state image pickup device or semiconductor device described in claim 1 wherein said first conductivity type is p type, while said second conductivity type is n type.
 11. A solid-state image pickup device manufacturing method used for manufacturing a solid-state image pickup device formed by arranging plural photodiodes separated by pixel separating regions in an array comprising: forming a first semiconductor region of a second conductivity type on the principal surface of a semiconductor substrate of a first conductivity type; forming a pixel separating region of the first conductivity type to penetrate through said first semiconductor region to separate the adjacent regions of said photodiodes; forming a second semiconductor region of the second conductivity type, used to drain excess charge away from the junction surface, in the area between said semiconductor substrate and said first semiconductor region in the semiconductor substrate below said junction surface.
 12. The solid-state image pickup device manufacturing method described in claim 11 wherein said second semiconductor region is formed below said pixel separating region in the step of forming said second semiconductor region.
 13. The solid-state image pickup device manufacturing method described in claim 11 further comprising forming a third semiconductor region of the first conductivity type on the surface layer of said semiconductor region.
 14. The solid-state image pickup device described in claim 2 wherein a third semiconductor region of the first conductivity type is formed on the surface layer of the first semiconductor region.
 15. The solid-state image pickup device described in claim 7 further comprising a sixth semiconductor layer of the first conductivity type is formed on said second, third, and fourth semiconductor layers.
 16. The solid-state image pickup device described in claim 7 further comprising a seventh semiconductor layer of the second conductivity type that is electrically connected to said fifth semiconductor layer, and a prescribed voltage is applied to said fifth semiconductor layer.
 17. The solid-state image pickup device described in claim 8 further comprising a seventh semiconductor layer of the second conductivity type that is electrically connected to said fifth semiconductor layer, and a prescribed voltage is applied to said fifth semiconductor layer.
 18. The solid-state image pickup device or semiconductor device described wherein claim 2 said first conductivity type is p type, while said second conductivity type is n type.
 19. The solid-state image pickup device or semiconductor device described wherein claim 4 said first conductivity type is p type, while said second conductivity type is n type.
 20. The solid-state image pickup device or semiconductor device described wherein claim 6 said first conductivity type is p type, while said second conductivity type is n type. 